No problem. Look at the license, I allow almost all of my pictures to be used for noncommercial purposes for free without asking abot permission. If you want use it commercial way, just ask, I have never said "no" to anyone who wanted my space art.

beside the colours and the general picture, I also like the diagonal composition: planets, light, background. the contrast between the dark and lighten sides of the planet was the first thing that caught my attention.

In short, I download about five-ten textures form here [link] (bigger texture = better texture ). Blend all I download into one quite big, size about 7000x7000 pixels... then spherize it, colorize, finally add some light effects and it is all. It is a bit time consuming due to size of textures but it is quite easy